A standard lathe has a bed at one end of which there is provided a headstock connected to a drive and at the other end there is a tailstock which can be moved longitudinally toward and away from the headstock to accommodate workpieces of different lengths. Such a lathe is used to machine mainly the center regions of a workpiece.
A center-drive lathe has, however, a bed at the center of which is provided a longitudinally nondisplaceable driven headstock or so-called centerstock, with to each longitudinal side a respective carriage provided with a tailstock or so-called endstock that may hold the end of the workpiece or may hold a tool that is used on the rotating workpiece. Both endstock carriages are movable along to the rotation axis, which corresponds to the longitudinal axis of the machine, toward and away from the centerstock. Such a machine is used mainly to machine the ends of a workpiece.
As described in German Pat. No. 3,620,231 such a machine normally has an inclined bed. The endstocks ride on rails underneath the bed and the slot through which the endstocks project must be covered to prevent chips, shavings, and the like from getting into the works of the machine and fouling the guides of the endstocks. To this end a system of stacked telescoping plates is used to each side of the centerstock with the plate at the top or bottom of the stack having an outer edge connected to the centerstock and the opposite end plate having its outer end connected to the respective endstock. Thus as an endstock is moved out it pulls the stack out and expands it, and as it moves in it telescopes the stack together.
In order to be able to work as close as possible to the centerstock it is necessary to make the stack as compact as possible. Thus as described in French Pat. No. 2,557,483 the stack is made of plates that are in fact of shorter longitudinal than transverse dimension. Such a system still places a lower limit equal to the longitudinal dimension of one of the plates on the working spacing. In addition such narrow plates are hard to guide and control so that they frequently cant and jam, and the large number of plates needed means that there are a large number of joints where shavings and the like can get in and jam the system.